When launching a boat from a trailer, the boat trailer is backed down the launching ramp to a position where the trailer lights will normally be submerged in the water. With the conventional boat trailer light, as used in the past, water enters the trailer light when the lights are submerged and contacts the light bulb and socket. Over a period of time, with repeated launchings, the contact of the bulb and socket with the water, particulary in salt water areas, will rapidly corrode the socket making it very difficult, if not impossible, to remove the bulb from the socket for replacement. As a further problem, during night launching or when waiting at a launching site, the bulbs may be lit for extended periods of time. When the trailer lights are then submerged, the cold water contacting the hot bulb may break the bulb, requiring replacement.
In an attempt to overcome the corrosion and breakage problems of trailer lights it has been proposed to fully seal the lens to the housing of the tail light through gaskets to prevent water from entering the housing when the light is submerged. However, the sealed tail light construction is relatively expensive and extreme care must be taken to properly seal the lens to the housing on replacement of the bulb.
To eliminate the problems in connection with the fully sealed tail light, tail lights have been marketed which operate on the air entrapment principle. As disclosed in U.S. Pat. No. 3,106,349 the bulb socket and bulb are located within the upper end of a housing, the upper end of which sealed and the lower end is open. When the light is submerged in water, air will be entrapped in the upper portion of the housing preventing the water from rising to a level where it will contact the bulb or socket.
U.S. Pat. No. 3,858,039 describes an improvement to the basic tail light operating on air entrapment principles. In this latter patent, the bulb and socket are mounted on a slide that can be removed from the lower open end of the housing to facilitate replacement of the bulb.